erica edwards kicks off our coverage >> reporter: nearly a third of the u.s. population living in areas with heat adadvisories today it was 128 but pair these record-breaking heat waves with record-setting wildfires in canada. at one point, new york city with the worst air quality in the world. >> outside right now, a picture that is simply other worldly >> reporter: it's making many americans struggle to catch their breath >> it's definitely a point of concern to have a combination of poor air quality and intense heat >> reporter: the risk of early death increases by 21% on days with extreme heat and air pollution, according to a 2022 study. so what exactly happens to your body when it's hit with both besides dehydration, heat takes a toll on your heart blood vessels get smaller and decrease the flow of oxygenated blood to your tissues and organs to compensate, your heart starts beating faster pushing blood pressure up. add in poor artir quality >> less movement of the air. >> reporter: your respiratory mucosal cells lie in your airways. normally, they make a

erica edwards takes us inside a cdc lab studying the bugs and how to stop them >> this is where we raiseos. >> reporter: inside this cdc lab in fort collins, colorado, swarms of mosquitos. >> probably tens of thousands of individual mosquitos. >> i'm glad we're suited up, then. >> reporter: boxed in, bottled up and studied, all in an effort to control an epidemic. >> west nile virus is one that really is endemic in the u.s. right now. >> reporter: the debilitating disease is a major concern for the cdc. mosquitos are becoming stronger than the chemicals meant to kill them. >> we have seen resistance across the country. >> reporter: that's what they're testing, finding in some cases the bugs are becoming immune to insecticides. >> it's like antibiotic resistance >> reporter: repellants, however, still work well watch as connolly sticks her arm into this cage filled with mosquitos. >> are they biting >> not yet. >> reporter: you can see them swarming her arm, but after a spray the bugs steer clear. >> there is not a single mosquito on you. >> right that's what we want and expect out of a r

. >> reporter: erica edwards, nbc news >>> the grand jury investigating efforts to subvert the 2020 presidential election heard hours-long testimony from a former trump white house aide yesterday. william russell is seen pictured with then-president trump on january 6, 2021. he spoke before the same special counsel prosecutor whose informed mr. trump he was the target of their investigation meaning he is likely to be indicted former trump attorney rudy giuliani met with prosecutors earlier this year, according to one of his advisors. the former new york city mayor was a key figure in the efforts to overturn the 2020 election. in washington, speaker mccarthy denied a report that he had promised m trump a house vote to expunge his two impeachments the former president denied breaking the law and has slammed many investigations into him as quote, a big and vicious witch-hunt bit left. >>> in another case connected to january 6, a former appointee in trump's state department was convicted thursday of seven felonies federico klein was found guilty on charges of obstruction of a proceeding, civil diso